WARSAW — Vice President Pence saluted the Polish people Sunday as they commemorated the 80th anniversary of the outbreak of World War II, praising their courage during the “five decades of untold suffering and death that followed.”

“It is difficult for any of us who are not Poles to fathom the horrors that began here 80 years ago, on this day, the first of September 1939,” Pence said solemnly, speaking in Pilsudski Square.

He added, “While the hearts of every American are with our fellow citizens in the path of a massive storm, today we remember how the gathering storm of the 20th century broke into warfare and invasion followed by the unspeakable hardship and heroism shown by the Polish people.”

As he recalled those sacrifices of the Polish people, Pence also remembered the “16 million Americans who left the peace and comfort of home to fight, to liberate Europe.”

It has been 80 years since Nazi Germany invaded Poland, sparking a conflict that wreaked devastation across Europe.

President Trump had planned to make his second official visit to Poland this weekend and speak at the commemoration but last week asked Pence to attend in his place because of Hurricane Dorian.

German Chancellor Angela Merkel and Ukrainian President Volodymyr Zelensky attended the ceremony, along with other European officials. Russian President Vladimir Putin was not invited following tensions with Polish leaders.

Pence and Zelensky, a former comedian who was elected in April, met later Sunday. Pence did not respond to questions from reporters at the top of the meeting, including questions about whether the Trump administration would still allocate $250 million in planned security aid to Ukraine, which is being reconsidered, according to U.S. officials.

But as national security adviser John Bolton looked on, Pence broadly assured the Ukrainian president that “we will continue to stand with the people of Ukraine on your security, on territorial integrity, including Ukraine’s rightful claim to Crimea.”

Attendees at the commemoration gathered in the sprawling square, waving Polish flags as a marching band played and soldiers marched. There was some scattered support for Trump’s reelection campaign in the crowd, with one “Trump 2020” banner visible.

Pence’s speech was heavy on themes of freedom and faith, quoting Pope John Paul II, who visited the same square during his historic trip to Poland in 1979, and Aleksandr Solzhenitsyn, the Soviet dissident and author.

The Polish experience since World War II, Pence said, proves “where the spirit of the Lord is, there is freedom.”

Pence criticized the “twisted ideologies of Nazism and Communism” in which, he said, “all morality became socialist morality. Whatever served the power of the state and its slave masters became justified, even murder on an unprecedented scale.”

He also called out the “unspeakable evil of the Holocaust” that “systemically murdered more than 3 million of Poland’s Jewish citizens.”

Hovering over Pence’s visit, however, is a friction point: Poland remains the only country in the European Union that does not have comprehensive legislation to deal with the restitution of private property confiscated by the Nazis — and, in Poland’s case, later nationalized under communist rule.

The Trump administration has been slow to call out Poland’s nationalist government as it chips away at democratic institutions, breaches the country’s constitution and spurs anti-LGBTQ sentiment. Most recently, the country’s deputy justice minister was forced to resign after it emerged that his ministry had waged a harassment campaign against judges resisting government efforts to control the judiciary.

But the Trump administration has weighed in on the issue of restitution of Jewish property, a matter that is politically fraught in Poland. Earlier this month, a bipartisan group of 88 senators led by Marco Rubio (R-Fla.) and Tammy Baldwin (D-Wis.) urged Secretary of State Mike Pompeo to press Poland to settle the issue.

A White House official said last week that Pence hopes to come to an agreement with the Polish government in meetings Monday about cybersecurity and the next-generation 5G wireless network.

Amid a trade dispute with China, the Trump administration has pushed European nations to punish Huawei, the Chinese telecommunications giant, on national security grounds.

Pence is scheduled to have a bilateral meeting with Polish President Andrzej Duda on Monday. Other issues on the agenda include the planned increase of U.S. troops in Poland, which has riled Russia, and visa requirements for Poles traveling to the United States.

Robert CostaRobert Costa is a national political reporter for The Washington Post. He covers the White House, Congress, and campaigns. He joined The Post in January 2014. He is also the moderator of PBS's "Washington Week" and a political analyst for NBC News and MSNBC. Follow